The present invention relates generally to water treatment apparatus, and more particularly to an improved high pressure oxygen-saturated water treatment apparatus for providing super-saturated oxygen treatment to waste water. Such apparatus may find a wide variety of usages in the treatment of waste water containing human waste, rejuvenation of swamps, cleansing water for catfish farming, or for agriculture, and/or during mining operations and for a wide variety of usages where it is desirable to purify waste water, or to provide oxidizing and entraining bubbles of oxygen about solid particulate material.
Governmental authorities and others have been making sustained efforts in recent years to limit the volumes and strengths of waste water discharges to bodies of water, such as lakes, rivers and streams. The largest source of contamination of these bodies of water is the category of wastes known as deoxygenating wastes. These materials, which include human sewage as well as certain types of industrial waste water, are typically high in their biochemical oxygen demand, and in their suspended solids levels.
Sewage treatment plants are concerned for the most part with effecting substantial reductions in biochemical oxygen demand and suspended solids levels of raw sewage and industrial waste water before the treatment plant effluent is discharged to a river or the like. Pollution control regulations in effect throughout the United States set limits on permissible levels of biochemical oxygen demand and suspended solids that will be tolerated. Sewage treatment personnel, and industrial waste water treatment firms, are continuously alert for more efficient and economical ways of reducing the concentration and quantity of biochemical oxygen demand containing materials in waste water.
One area which has previously been investigated to some extent involves creation of oxygen-enriched clean water, followed by contact of the oxygen-enriched water with waste water to be treated. The excess oxygen in the enriched water brings about rapid degradation of the wastes, and thereby cleanses the waste water to acceptable contaminant levels.
As indicated, the present invention is concerned with provision of an oxygen-enriched water stream useful for contacting and for the resultant cleansing of waste water. Typically, the waste water to be treated contains suspended solids along with dissolved inorganic and organic contaminants. These contaminants represent a high demand for any available oxygen. Thus, the waste water has relatively high biochemical oxygen demand and relatively high chemical oxygen demand, which are parameters of the polluting characteristics of the waste water.
Upon contact of the waste water with an oxygen enriched water stream, the contaminants of the waste water tend to undergo oxidation. The oxygen-enriched stream tends to satisfy the oxygen demand of the waste water. Thus, the inorganic contaminants oxidize to less soluble oxides, while the organic components are converted to carbonaceous residues and carbon dioxide. The insolublized components then generally rise to the surface of the waste water where they may be removed by any of several techniques, such as surface skimming, for example, which are known to those of ordinary skill in the art.
The gas-liquid combination system of the present invention, which generates the oxygen-enriched cleansing water, utilizes in a novel manner several well-known physical principles. The principal mechanisms by which the oxygen-enrichment is created are believed to be through diffusion and dissolution of the oxygen component of air in water. In the process of diffusing air in water, the system relies on both Henry's Law and Dalton's Law of Partial Pressures.
Under Henry's Law the amount of gas dissolved in a liquid is directly proportional to the pressure of the gas. At standard temperature and pressure (1 atm. at 20 degrees C.), the solubility of air in water is approximately 24. mg/liter. This relationship is linear at constant temperature--i.e., as the pressure increases, so does solubility. As the temperature changes, so does the solublity. The rate of dissolution is inversely proportional to temperature, and approaches zero at both the boiling and freezing points of water. The highest rate of gas dissolution occurs at approximately 4 degrees C., below which temperature the solubility rapidly approaches zero.
Since air is a mixture of gases (approximately 79 percent nitrogen, 20 percent oxygen, and 1 percent rare gases and contaminants), the partial pressure of each gas must be evaluated using Dalton's Law of Partial Pressures. According to this Law, the total pressure of a confined gas mixture equals the sum of the pressures each gas would exert alone in the same volume.
Applying Dalton's Law to the oxygen (molecular weight 16) and nitrogen (molecular weight 14) contents of air, and combining these results with the application of Henry's Law, the following maximum solubilities of these gases in water (at standard temperature of 20 degrees C.) are found:
______________________________________ Gas Pressure Dissolved Air Molecular Fraction psi mg/l O.sub.2 mg/l N.sub.2 mg/l ______________________________________ 14.7 24.0 4.8 19.2 20 33.6 6.7 26.9 40 100.8 20.1 80.7 60 168.0 33.5 134.5 80 235.2 46.9 188.3 100 302.4 60.3 242.1 120 369.6 73.7 295.9 140 436.8 87.1 349.7 ______________________________________
In a diffused solution, the dissolved gas tends to remain in solution so long as the equilibrium pressure remains undisturbed. Thus, the amount of oxygen dissolved in water in a sealed vessel at, for example 100 P.S.I., will tend to stay in the water until the diffused solution is discharged from the vessel into another vessel under lower pressure or into the atmosphere. Upon such reduction of the pressure to atmospheric, for example, some of the dissolved gas escapes and forms small microscopic-size bubbles (the gaseous form of lowest energy is spherical, hence the formation of bubbles). These bubbles behave in a way predictable by the Nucleus Theory, according to which a gas coming out of solution from a liquid tends to form bubbles of finite nuclei. This concept is used to advantage in utilization of the product of the present invention, as such bubbles tend to collect about small particles of solid material, in this case the suspended waste solids, to form larger particles of lesser specific gravity which tend to rise to the surface, resulting in clarification of the liquid. Such highly air-entrained waste can then readily be skimmed off for disposal.
Accordingly, it is one object of the improved high pressure oxygen-saturated water treatment apparatus of the present invention to provide apparatus which will provide super-saturated oxygen for mixing with waste water to remove suspended waste from such waste water.
It is also an object of the improved high pressure oxygen-saturated water treatment apparatus of the present invention to provide such super-saturated oxygen treatment under substantial pressure to be injected into a containment tank having a reduced pressure, and accordingly to permit such oxygen to come out of solution in the form of tiny bubbles around nuclei of such waste particles, whereby such waste particles may be entrained and floated to the surface.
It is a yet further object of the improved high pressure oxygen-saturated water treatment apparatus of the present invention to provide venturi means which will combine the pressurized oxygen-containing stream with recirculation waste water in a stream under pressure to form a combined injection stream of pressurized water which is super-saturated with oxygen, to be injected into treatment water contained within a treatment tank for substantially oxidizing the oxidizable material contained therewithin.
Upon further review of the specification hereof, additional objects and advantages of the present invention will become apparent to those of ordinary skill in the art.